He's playing baseball, contributing to his team, and having fun doing it.

The Pirates dealt veteran shortstop John McDonald to the Indians for a player to be named or cash earlier this week, so it looks like Mercer is here to stay after bouncing between Triple-A Indianapolis and Pittsburgh earlier this year.

Mercer had three hits and two runs Wednesday night in the Pirates' 12-8 win, and he entered Thursday batting .278 with three homers, six RBIs and nine runs in 79 at-bats. The key to his success, he says, is just staying loose.

"You just go out and play your game, you have fun like a little kid," Mercer said. "You get all the worries and everything out."

Mercer started Thursday night against the Giants --- playing behind sinkerballer Charlie Morton, who is known for keeping middle infielders busy with ground balls. Pirates manager Clint Hurdle is confident in Mercer's defense and bat and started him against righty Matt Cain and over veteran Clint Barmes, somewhat of a defensive specialist.

"He's brought more to the table. His confidence level has never been higher," Hurdle said of Mercer. "His game has been fresh, his game is solid. So we have a lot of confidence. He's finishing games. How much more confidence can we have in a guy that's finishing games at shortstop?"

Mercer is hitting just .214 against righties this season, but Hurdle said he wants to get the Oklahoma State product in the lineup if he's going to be with the big league club. He is 10-for-23 with three homers and four RBIs against lefties this year.

Mercer is just relishing this opportunity, always with a smile on his face. And that's what playing baseball is all about to him.

"It's still a dream come true for me," he said. "It's something that you dream about as a little kid playing in the backyard. You hope to excel one day, and now that I'm getting the chance to do it, it's pretty special."